1. Field of the Invention
The present invention relates to a slice image creation device, a three-dimensional printing system, and a slice image creation method.
2. Description of the Related Art
Conventionally, a three-dimensional printing device that prints a desired three-dimensional object (hereinafter, referred to as a “target object”) is known. This type of three-dimensional printing device uses, for example, a computer-aided design device (hereinafter, referred to also as a “CAD device”) to create data on a three-dimensional model which is usable to print the target object (hereinafter, such a three-dimensional model will be referred to as a “target object model”) (see, for example, Japanese PCT National-Phase Patent Publication No. 2003-535712). The target object model is sliced at a predetermined interval to create a plurality of two-dimensional slice models corresponding to cross-sectional shapes of the target object (hereinafter, such a two-dimensional slice model will be referred to as a “target slice model”).
A target slice model is defined by a contour of the target object. The target slice model is divided into a printing region, which is to be printed, and a non-printing region, which is not to be printed, along the contour of the target object. Thus, for example, the printing region in the region of the target slice model is colored white and the non-printing region is colored black by the CAD device, so that a slice image (hereinafter, referred to as a “target slice image”) is created from the target slice model.
A three-dimensional printing device includes, for example, a table provided with an opening, a tank that is located on the table and accommodates a photocurable resin, a holder that is located above the tank and is movable up and down, and an optical device that is located below the table and outputs light. Light that is output from the optical device is directed toward the photocurable resin in the tank through the opening in the table. A portion of the photocurable resin, accommodated in the tank, that is irradiated with the light is cured. The position to be irradiated with the light is controlled to appropriately change the position of the photocurable resin to be cured, so that a portion of the photocurable resin located in the region colored white, in the target slice image, is cured whereas a portion of the photocurable resin located in the region colored black is not cured. As a result, a cross-sectional shape conformed to the target slice image is formed. The holder is sequentially moved up to continuously expand the resin layer downward. In this manner, a desired target object is printed.
While the holder is sequentially moved up, a certain resin layer supports the load of all the resin layers below the certain resin layer. Therefore, in the case where, for example, there is a resin layer having a small cross-sectional size, such a resin layer may not be able to support the load of all the resin layers printed below the resin layer. This may result in a portion of the target object being destroyed in the middle of the printing operation of the target object. For example, it is assumed that a target object 170 shown in FIG. 10A and FIG. 10B is to be printed. The target object 170 includes a first object 170a and a second object 170b having different sizes. The first object 170a and a second object 170b are located adjacent to each other. Referring to FIG. 11, in order to prevent a portion of the target object 170 from being destroyed during the printing operation, a plurality of support objects 130 are attached and arranged between a portion of the target object 170 and a holder 113. The plurality of support objects 130 support a portion of the load of the target object 170 during the printing operation. The plurality of support objects 130 are provided by a computation performed by a dedicated device such as a CAD device or the like. In this manner, an object 180 including the target object 170 (assembly of the first object 170a and the second object 170b) and the support objects 130 in an integral manner is printed (hereinafter, an object such as the object 180 will be referred to as a “whole object”). In the following description, the support objects will be referred to simply as “supports”.
FIG. 12 shows a two-dimensional slice model 182 obtained as a result of slicing a three-dimensional model corresponding to the whole object 180 at position PT100 in FIG. 11. For printing the whole object 180 as described above, the CAD device slices a three-dimensional model corresponding to the whole object 180 (hereinafter, such as three-dimensional model will be referred to as a “whole object model”) at a predetermined interval to create a plurality of the two-dimensional slice models 182 as shown in FIG. 12 (hereinafter, such a two-dimensional slice model will be referred to as a “whole slice model”). A printing region and a non-printing region of the whole slice model 182 are colored with different colors to create a slice image from each of the whole slice models 182 (hereinafter, the slice image created from the whole slice model will be referred to as a “whole slice image”). The slice image includes a contour that distinguishes the printing region and the non-printing region from each other. The slice image includes a multiplexed portion where, for example, a plurality of contours cross each other. The contour that distinguishes the printing region and the non-printing region from each other is one of the plurality of contours in the multiplexed portion. Usually, an outermost contour is the contour that distinguishes the printing region and the non-printing region from each other. Extracting such a contour will be occasionally referred to as “peeling”.
However, the whole slice model 182 may include, in a mixed state, a contour 173a of a slice model 172a of the first object 170a (hereinafter, the slice model of the first object 170a will be referred to as the “first target slice model”), a contour 173b of a slice model 172b of the second object 170b (hereinafter, the slice model of the second object 170b will be referred to as the “second target slice model”), and contours 133 of a support slice model 132 obtained as a result of slicing the supports 130 at a predetermined interval. Thus, before creating the whole slice image, the CAD device traces the contours to obtain a contour that distinguishes the printing region and the non-printing region of the whole slice model 182 from each other (peeling), among the contour 173a of the first target slice model 172a, the contour 173b of the second target slice model 172b, and the contours 133 of the support slice model 132. For example, as shown in FIG. 12, the whole slice model 182 includes an intersection 184 at which the contour 173a, the contour 173b and a contour 133a cross each other. In the case where the CAD device traces the contour 173a as represented by the arrow in FIG. 12, the CAD device transfers from the contour 173a to the contour 133a at the intersection 184. However, at the intersection 184, there are a plurality of candidate contours to which the CAD device may transfer. Specifically, at the intersection 184, there are two contours to which the CAD device may transfer, namely, the contour 173b and the contour 133a. Therefore, there is a risk that the CAD device may transfer to the contour 173b despite that the CAD device should transfer to the contour 133a. When this occurs, the CAD device does not perform the desired peeling for the whole slice model 182 correctly, and thus may not create a desired whole slice image.